In order to fully understand baptism in the New Testament, we have to begin with John’s baptism. John the Baptist prepared the way for Jesus, calling people to repentance and baptizing them: “Then in Jerusalem and all Judea and all the region about the Jordan were going out to him, and they were baptized by him in the river Jordan, confessing their sins” (Matthew 3:5-6 ESV). We know that it was a baptism of repentance when Paul asked a group of new converts in Ephesus if they received the Holy Spirit when they believed. They said they had not even heard there was a Holy Spirit. When Paul asked what they were baptized into, they replied, “John’s baptism.” Paul said, “John baptized with the baptism of repentance, telling people to believe in the one who was to come after him, that is, Jesus” (Acts 19:4). After hearing this, the new converts were re-baptized and then received the Holy Spirit.
Jesus, having no sin, was baptized by John. If John’s baptism was a baptism of repentance, why was Jesus baptized? When John questioned why Jesus felt the need to be baptized by him, he replied, “Let it be so now, for thus it is fitting for us to fulfill all righteousness” (Matthew 3:15). Unlike John’s other baptisms, the Holy Spirit descended on Jesus immediately after his baptism (vs. 16). John prepared the way for Jesus by baptizing for repentance but Jesus fulfilled all righteousness by being baptized.
But after Jesus died and was raised, the Christian baptism now took effect. Hebrews 9:17 gives us a clue into why John’s baptism shifted after Jesus died: “For a will takes effect only at death, since it is not in force as long as the one who made it is alive.” We see the change in language immediately after Jesus died and was raised when Peter explained, “Repent and be baptized every one of you in the name of Jesus Christ for the forgiveness of your sins, and you will receive the gift of the Holy Spirit” (Acts 2:38). In order for Christ’s will to go into effect he had to both die and be raised: “Indeed, under the law almost everything is purified with blood, and without the shedding of blood there is no forgiveness of sins” (Hebrews 9:22).
Hebrews tells us that under the old covenant blood had to be shed over and over again. But when Christ died his blood covers believers completely through Christian baptism.